青藏高原东缘汶川地震断层陡坎类型与级联破裂模型(英文)

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英文篇名：Fault-scarp features and cascade-rupturing model for the Wenchuan earthquake (M_W7.9),eastern Tibetan Plateau, China 中文刊名：国际地震动态 英文刊名：Recent Developments in World Seismology 作者：徐锡伟 ; Yann Klinger 英文作者：Guihua Yu1) ; Xiwei Xu1) National Center for Active Fault Studies ; Institute of Geology ; CEA ; Beijing 100029 2) Institut de Physique du Globe de Paris ; CNRS-INSU ; Paris 3) Earthquake Administration of Hebei Province ; Shijiazhuang 050021 4) Earthquake Administration of Shanghai Municipality ; Shanghai 200062 出版日期：2010-06-25 机构：National Center for Active Fault Studies, Institute of Geology, CEA;Institut de Physique du Globe de Paris,CNRS-INSU, Paris; 年：2010 期：06 出版单位：国际地震动态

摘要

The post-earthquake field investigations reveal that the MW7.9 Wenchuan earthquake of 12th May 2008 ruptured three NE-striking imbricate reverse faults and another NW-trending reverse fault, along the middle Longmenshan fold-and-thrust belt at the eastern margin of the Tibetan plateau. The fault-scarp features can be categorized into eight groups: simple thrust scarp, hanging-wall collapse scarp, simple pressure ridge, dextral pressure ridge, fault-related fold scarp, back-thrust pressure ridge, local normal fault scarp and crocodile-mouth-like scarp. The local normal scarp is first discovered in the reverse-faulting earthquakes as ever reported in the world. Field observation indicates that the Wenchuan earthquake surface rupture is dominated by reverse faulting with a minus right-lateral component, but the relative ratio varies from site to site. Also, the surface ruptures can be divided, for the first order, into two segments, the Yingxiu and Beichuan segments, corresponding to MW7.8 and MW7.57 events, respectively. The two segments further can be divided, for the second order, into four sub-segments in total, which are equivalent to four sub-events of MW7.46, MW7.69, MW6.99 and MW7.52, respectively. The fault segmentation, for different orders, shows a cascade-rupturing pattern and can explain why the quake time of the Wenchuan earthquake was so long as up to 100 second. Aftershock focal mechanisms are also used to constrain the fault geometry for the sub-segments, indicating that the seismogenic faults are listric at depth and in general, the fault plane becomes steeper northward, which enables the fault to accommodate larger strike-slip motion. This earthquake also confirms that the crustal shortening across the Longmenshan fold-and-thrust belt should be responsible for the growth of high topographic relief along the eastern margin of the Tibetan Plateau.

引文